Add an incremental SHA-256 library for the browser and node tests

frontend/sha256.test.js

@@ -0,0 +1,45 @@
+'use strict';
+const { test } = require('node:test');
+const assert = require('node:assert');
+const crypto = require('node:crypto');
+const Sha256 = require('./sha256');
+
+const ref = (buf) => crypto.createHash('sha256').update(buf).digest('hex');
+
+test('known vectors', () => {
+  assert.strictEqual(Sha256.hex(new Uint8Array(0)), 'e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855');
+  assert.strictEqual(Sha256.hex(new TextEncoder().encode('abc')), 'ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad');
+  assert.strictEqual(
+    Sha256.hex(new TextEncoder().encode('abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq')),
+    '248d6a61d20638b8e5c026930c3e6039a33ce45964ff2167f6ecedd419db06c1');
+});
+
+test('every length around block boundaries matches node:crypto', () => {
+  for (let n = 0; n <= 200; n++) {
+    const buf = crypto.randomBytes(n);
+    assert.strictEqual(Sha256.hex(new Uint8Array(buf)), ref(buf), 'length ' + n);
+  }
+});
+
+test('random chunk boundaries give the same digest as one shot', () => {
+  const buf = crypto.randomBytes(3 * 1024 * 1024 + 17);
+  for (let round = 0; round < 5; round++) {
+    const h = Sha256.create();
+    let pos = 0;
+    while (pos < buf.length) {
+      const n = Math.min(buf.length - pos, 1 + Math.floor(Math.random() * 200000));
+      h.update(new Uint8Array(buf.buffer, buf.byteOffset + pos, n));
+      pos += n;
+    }
+    assert.strictEqual(h.hex(), ref(buf));
+    assert.strictEqual(h.bytes, buf.length);
+  }
+});
+
+test('update after digest throws; isHex', () => {
+  const h = Sha256.create();
+  h.hex();
+  assert.throws(() => h.update(new Uint8Array(1)));
+  assert.ok(Sha256.isHex(ref(Buffer.from('x'))));
+  assert.ok(!Sha256.isHex('ABC'));
+});